ITU-R (International Telecommunication Union Radio communication sector) is standardizing an IMT (International Mobile Telecommunication)-Advanced, a next-generation mobile communication system following the 3rd generation mobile communication system. The IMT-Advanced aims to support IP (Internet Protocol)-based multimedia services at a data transfer rate of 1 Gbps in a stationary and low-speed movement state and at a data transfer rate of 100 Mbps in a high speed movement state.
3GPP (3rd Generation Partnership Project) is preparing a system standard satisfying the requirements of IMT-Advanced, which is LTE (Long Term Evolution)-Advanced improving LTE which uses OFDMA (orthogonal frequency division multiple access)/SC-FDMA (single carrier-frequency division multiple access). The LTE-Advanced is one of potential candidates for IMT-Advanced. A major technique of the LTE-Advanced includes a relay station technique.
A relay station, a device relaying a signal between a base station (BS) and a user equipment (UE), is used to extend a cell coverage of a wireless communication system and improve throughput.
A 3GPP LTE system was designed without taking a relay station into consideration. In order to operate the relay station, various matters such as synchronization with the BS, a radio resource allocation, and the like, must be considered. The LTE-A system is designed based on backward compatibility with an LTE system, so in order for the relay station to be introduced to the LTE-A system, an operation with a UE supporting only the existing LTE needs to be considered.